Defence personnel in Darwin were operating at “increased readiness” earlier this month as Russian strategic bombers conducted navigation exercises close to Australia, flying out of an Indonesian military base.

Key points:

RAAF Base Darwin placed on a “short period” of heightened alert

Russian Ministry of Defence claims it “carried out air alert mission over neutral waters of south Pacific Ocean”

Defence Department would have been concerned about Russian intelligence collection, defence expert says

The ABC can reveal RAAF Base Darwin was placed on a “short period” of heightened alert, while over 100 Russian personnel and several aircraft were stationed at the Biak Airbase in Indonesia’s eastern Papua province.

During the five-day stopover two nuclear-capable Tu-95 bombers flew their first ever patrol mission over the South Pacific, prompting concerns they may have been collecting valuable intelligence.

The Russian Ministry of Defence claims its strategic bombers “carried out air alert mission over neutral waters of south Pacific Ocean” in a flight lasting more than eight hours.

In a statement to the ABC, Australia’s Defence Department said “the ADF maintains appropriate levels of readiness and posture to respond to evolving circumstances,” but did not specifically refer to the Russian activity.

“There were no instances of unalerted or unscheduled foreign aircraft operating in Australian airspace during this period,” the Department added.

Defence also insists RAAF Base Darwin was never in lockdown, but did acknowledge “in early December there was a brief period of…